During a vehicle start operation, it may be advantageous to provide fuel pressure to the fueling system of the engine as fast as possible, especially in a direct injection engine system. Various approaches have been described to achieve such a feature.
While low pressure (e.g., port injection) single speed (single pump voltage) mechanical returnless fuel systems may achieve lift pump operation with no minimal delays in application of the fuel lift pump using a default, on-command, for the lift pump. However, such a lift pump system may operate ineffectively in higher pressure, direct injection systems since a single speed fuel system results in design tradeoffs that injure lift pump durability and increase lift pump energy consumption. Thus, variable speed/voltage pumps have been applied in direct injection applications.
Furthermore, when using a variable speed electronically controlled pump in direct injection applications, prior approaches have utilized a default, off-command, for the pump to address various degradation conditions (so that inadvertent pump operation is less likely to occur). However, this default-off state adds to delays in providing sufficient fuel pump pressure, since various systems must first initialize before the fuel pump may be reliably activated. Other solutions use complex wiring and communications between the PCM and lift pump control module to achieve the goal of rapid lift pump voltage application with favorable behaviors in degraded states.
The inventors herein have recognized the above issues, and attempted to address the conflicting requirements of the prior art, in one embodiment, by a method for controlling a fuel system of a vehicle. The method may comprise generating fuel pressure via an electronically controlled pump, the electronically controlled pump actuated responsive to a command; during an initial start-up duration, translating the fuel pump command via a first mapping to drive the fuel pump, where the first mapping includes mapping a default signal to active pump operation; and after the initial start-up duration, translating the fuel pump command via a second mapping to drive the fuel pump where the second mapping includes mapping the default signal to pump deactivation.
In one example, it is thus possible to provide a system that does not activate the fuel pump when a command is absent, avoids activating the fuel pump in response to various system degradation conditions, yet still provides variable speed pump operation with pump activation upon control system initialization without waiting for initialization of the control system. Note, however, that various other alternative and/or additional functions may be achieved. Further, note that various approaches may provide a first and second mapping, such as via an algorithm in a processor, an electrical circuit, etc. Further, note than the initial duration may include a time limit, or a non-time-based limit (e.g., it may include a limit related to a number of calculations performed by a processor, etc).